These terms are used in jewellery making and/or glass fusing. Where the meaning of a term is specific to one of these subjects this will be highlighted. Some terms may have multiple meanings.
| Carat | A measure of weight used for gemstones. 1 carat = 300 milligrams. The term carat being derived from the carob seeds used by early gem traders on the balance scales. The carob seed being very uniform in size. |
| Facet | One of the small flat surfaces of a faceted gemstone. |
| Inclusion | An internal flaw in a gemstone that can reduce the clarity. |
| Octahedron | A polyhedron with eight faces, twelve edges, and six vertices |
| Pavilion | That part of a gemstone below the girdle. |
| Point | When referring to gemstones, this is a measure of weight. There are 100 points per carat. |
| Polyhedron | A solid in three dimensions with flat polygonal faces, straight edges and sharp corners or vertices. |
